U.S. patent application number 15/448318 was filed with the patent office on 2018-12-13 for blade tip seal.
This patent application is currently assigned to Rolls-Royce Corporation. The applicant listed for this patent is Rolls-Royce Corporation. Invention is credited to CHRISTOPHER HALL, M. Stephen Krautheim.
Application Number | 20180355732 15/448318 |
Document ID | / |
Family ID | 64563301 |
Filed Date | 2018-12-13 |
United States Patent
Application |
20180355732 |
Kind Code |
A1 |
HALL; CHRISTOPHER ; et
al. |
December 13, 2018 |
BLADE TIP SEAL
Abstract
A blade tip sealing portion forms the distal end of a rotor
blade in a turbine engine to reduce or prevent leakage through the
blade tip clearance. A rotor assembly comprises a casing, a rotor,
and at least one rotor blade coupled to the rotor. The rotor blade
comprises a root portion coupled to the rotor, a main airfoil body
extending radially from the root portion, and a blade tip sealing
portion. The blade tip sealing portion comprises a blade tip
platform and a plurality of sealing members. The sealing members
are positioned on the blade tip platform at an angle substantially
perpendicular to an air flow across the blade tip platform and are
spaced to effect overlap of adjacent sealing members in the
direction of the air flow.
Inventors: |
HALL; CHRISTOPHER;
(Indianapolis, IN) ; Krautheim; M. Stephen;
(Fountaintown, IN) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Rolls-Royce Corporation |
Indianapolis |
IN |
US |
|
|
Assignee: |
Rolls-Royce Corporation
Indianapolis
IN
|
Family ID: |
64563301 |
Appl. No.: |
15/448318 |
Filed: |
March 2, 2017 |
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
F01D 11/122 20130101;
F05D 2250/182 20130101; F05D 2220/323 20130101; F05D 2250/181
20130101; F05D 2240/307 20130101; F01D 5/20 20130101; F05D 2240/11
20130101 |
International
Class: |
F01D 5/20 20060101
F01D005/20; F01D 11/12 20060101 F01D011/12 |
Claims
1. A rotor assembly comprising: a casing; a rotor encased by said
casing; and at least one rotor blade coupled to said rotor, said
rotor blade comprising: a root portion coupled to said rotor; a
main airfoil body extending radially from said root portion, said
airfoil body comprising a pressure side surface and a suction side
surface joined at and extending between a leading edge and a
trailing edge; and a blade tip sealing portion forming a distal end
of said rotor blade, said blade tip sealing portion comprising: a
blade tip platform facing said casing and extending at least
between distal edges of said pressure side surface and said suction
side surface of said main airfoil body; and a plurality of sealing
members extending radially from said blade tip platform, said
sealing members being positioned on said blade tip platform to
extend between a pressure side edge and a suction side edge at an
angle substantially perpendicular to an air flow across said blade
tip platform and being spaced between said leading edge and said
trailing edge of said main airfoil body to effect overlap of
adjacent sealing members in the direction of the air flow.
2. The rotor assembly of claim 1 wherein the sealing members are
positioned to effect greater spacing between the members near the
edges of the blade relative to the spacing between members near the
mid-chord of the blade.
3. The rotor assembly of claim 1 wherein the sealing members are
positioned to effect greater spacing between the members near the
mid-chord of the blade relative to the members near the edges of
the blade.
4. The rotor assembly of claim 1 wherein the plurality of sealing
members have a uniform radial dimension.
5. The rotor assembly of claim 1 wherein the plurality of sealing
members have a differing radial dimension.
6. The rotor assembly of claim 1 wherein each of the plurality of
sealing members have a varying radial dimension along the length
thereof.
7. The rotor assembly of claim 1 wherein the elongated sealing
members are positioned to effect uniform spacing between the
members along the blade tip chord.
8. The rotor assembly of claim 1 wherein the elongated sealing
members are positioned to effect non-uniform spacing between the
members along the blade tip chord.
9. In a rotor assembly having a casing, a rotor encased by the
casing, and a rotor blade coupled to the rotor having a blade tip
spaced from the casing, a method of reducing a tip leakage air flow
between the blade tip and the casing from a pressure side of the
rotor blade to a suction side of the rotor blade during rotation of
the rotor, said method comprising: determining a primary direction
of the tip leakage air flow relative to a blade tip chord; and
positioning a plurality of elongated sealing members on a radially
outward facing surface of the blade tip, the sealing members being
positioned at an angle substantially perpendicular to the primary
direction of the tip leakage air flow and being spaced along the
blade tip chord to effect overlap of adjacent sealing members in
the direction of the tip leakage air flow.
10. The method of claim 9 further comprising: positioning a blade
tip platform over the blade tip, the blade tip platform having a
surface facing the casing and extending at least between the distal
edges of the pressure side and suction side of the blade and from
the midchord toward the leading edge and trailing edge of the
blade.
11. The method of claim 10 wherein said blade tip platform extends
to the leading edge and trailing edge of the blade.
12. The method of claim 9 wherein the elongated sealing members are
positioned to effect uniform spacing between the members along the
blade tip chord.
13. The method of claim 9 wherein the elongated sealing members are
positioned to effect non-uniform spacing between the members along
the blade tip chord.
14. The method of claim 13 wherein the elongated sealing members
are positioned to effect greater spacing between the members near
the edges of the blade relative to the spacing between members near
the mid-chord of the blade.
15. The method of claim 13 wherein the elongated sealing members
are positioned to effect greater spacing between the members near
the mid-chord of the blade relative to the members near the edges
of the blade.
16. The method of claim 9 comprising positioning wherein the
plurality of elongated sealing members have a uniform radial
dimension.
17. The method of claim 9 wherein the plurality of elongated
sealing members have a differing radial dimension.
18. The method of claim 9 wherein the plurality of elongated
sealing members each have a varying radial dimension along the
length thereof.
19. The method of claim 9 comprising: providing an abradable region
on the casing adjacent the blade tip; dimensioning the sealing
members in the radial direction to effect contact between at least
a portion of each sealing member and the abradable region; and
rotating the rotor to effect rub between the plurality of sealing
members and the abradable region, wherein said rub causes a
plurality of annular channels to be formed in the abradable region
with each one of said plurality of annular channels corresponding
to a respective one of said plurality of sealing members.
20. In a rotor assembly having a casing, a rotor encased by the
casing, and a rotor blade coupled to the rotor having a blade tip
spaced from the casing, a method of reducing a tip leakage air flow
between the blade tip and the casing from a pressure side of the
rotor blade to a suction side of the rotor blade during rotation of
the rotor, said method comprising: positioning a blade tip platform
over the blade tip, the blade tip platform having a surface facing
the casing and extending at least between distal edges of the
pressure side and suction side of the blade and between a leading
edge and a trailing edge of the blade; positioning a plurality of
elongated sealing members on the surface of the blade tip platform
having a selected lateral cross-sectional shape, the sealing
members being positioned at a selected angle relative to the blade
tip chord and being spaced in a selected chord-wise spacing pattern
along the blade tip chord; determining the flow rate and direction
of the tip leakage airflow; and varying one or more of the selected
lateral cross-sectional shape, the selected angle relative to the
blade tip chord, and the selected chord-wise spacing pattern to
effect a change in the flow rate of the tip leakage air flow.
Description
FIELD OF THE DISCLOSURE
[0001] The present invention relates generally rotor assemblies
having a casing around a rotor and blades such as a fan,
compressor, or turbine in a gas turbine engine and, more
specifically, to sealing the clearances between the blade tip and
casing in such rotor assemblies.
BACKGROUND
[0002] In a turbomachine such as a gas turbine engine, air acts as
the working fluid and is compressed by a fan, a compressor, or a
combination of the fan and compressor. The compressed air is mixed
with fuel and combusted in a combustor, and the combustion gases
are expanded through a turbine to extract energy. The extracted
energy may be used, for example, to generate electricity or to
rotate one or more shafts which may be coupled to the fan and/or
compressor. In applications where the turbine engine is providing
motive force to a vehicle such as an aircraft, combustion gases may
additionally be ejected from the turbine to provide thrust.
[0003] Each of the fan, compressor, and turbine comprise one or
more sets of blades attached about a rotatable shaft or a disc
which is coupled to a rotatable shaft. During operation, the blades
rotate with the shaft or disc. In the fan and compressor, the
rotation of the blades increases the pressure of the air;
conversely, in the turbine the rotation of the blades decreases the
pressure of the combustion gases and extracts work.
[0004] Each set of blades is typically circumferentially encased by
an engine casing or a shroud. FIG. 1 is a schematic and sectional
view of a portion of a blade 101 and casing 103. Due to various
operational transients such as but not limited to blade and case
expansion, maneuver deflections, transient overshoot, bearing and
damper clearances, general part tolerances, and axial excursions,
blades are typically designed with a blade tip clearance 105. A
blade tip clearance 105 is a gap between the radially inner surface
107 of the casing 103 and the tip 109 of a blade 101. Blade tip
clearance 105 may be calculated as the radius of the inner surface
107 minus the radius of the blade tip 109.
[0005] Although blade tip clearances 105 are a preferred method of
preventing contact between the blade tip and the casing (commonly
referred to as "rub"), which can lead to damage of the blade and/or
casing and even engine failure, blade tip clearances 105 are
problematic in that they result in leakage from a relatively high
pressure side of a blade to a relatively low pressure side of a
blade during operation. Stated differently, air or combustion gases
may leak from the pressure side of the blade to the suction side of
the blade. Such leakage generally decreases the efficiency of the
fan, compressor, and/or turbine, and may in some applications
result in decreased stall margin. The magnitude of the tip
clearance relative to the spanwise dimension of the airfoil
expressed as a percentage can be termed the clearance to span
ratio. A change in tip clearance for a large clearance to span
ratio, such as at the rear of a compressor, will be more impactful
to the efficiency aforementioned.
[0006] It is thus desirable to provide a system and method of
reducing leakage across the blade tip 109 while ensuring that a
rotating blade 101 does not contact the casing 103 in a manner that
will cause damage to the engine. Reducing blade tip leakage would
increase the efficiency of the fan, compressor, and/or turbine, and
may in some applications result in increased stall margin. Further,
reducing blade tip leakage may additionally allow for the
optimizing of additional aero and mechanical requirements such as
flow, pressure ratio, weight, and cost, among other variables.
[0007] The present application discloses one or more of the
features recited in the appended claims and/or the following
features which, alone or in any combination, may comprise
patentable subject matter.
SUMMARY
[0008] According to an aspect of the present disclosure, a rotor
assembly comprised of a casing, which encases a rotor, which is
coupled to at least one rotor blade comprised of a root portion, a
main airfoil body extending radially from the root portion. The
airfoil body is comprised a pressure side surface and a suction
side surface, joined at and extending between a leading edge and a
trailing edge, and a blade tip sealing portion, forming the distal
end of the rotor blade. The blade tip sealing portion is comprised
of a blade tip platform facing the casing and extending at least
between the distal edges of the pressure side surface and the
suction side surface of said the airfoil body. A plurality of
sealing members extends radially from the blade tip platform, and
are positioned on the blade tip platform to extend between a
pressure side edge and a suction side edge at an angle
substantially perpendicular to an air flow across the blade tip
platform, and are spaced between the leading edge and the trailing
edge of the main airfoil body to effect an overlap of adjacent
sealing members in the direction of the air flow.
[0009] In one embodiment the sealing members are positioned to
effect greater spacing between the members near the edges of the
blade relative to the spacing between members near the mid-chord of
the blade. In another embodiment the sealing members are positioned
to effect greater spacing between the members near the mid-chord of
the blade relative to the members near the edges of the blade. In
yet another embodiment the plurality of sealing members may have a
uniform radial dimension. An embodiment may also consist of the
plurality of sealing members may have a differing radial dimension.
In another embodiment each of the plurality of sealing members may
have a varying radial dimension along the length thereof. In yet
another embodiment the elongated sealing members are positioned to
effect uniform spacing between the members along the blade tip
chord. A final embodiment may comprise of elongated sealing members
positioned to effect non-uniform spacing between the members along
the blade tip chord.
[0010] Another aspect of the disclosure regarding a rotor assembly
having a casing, a rotor encased by the casing, and a rotor blade
coupled to the rotor having a blade tip spaced from the casing, may
be a method of reducing a tip leakage air flow between the blade
tip and the casing from a pressure side of the rotor blade to a
suction side of the rotor blade during rotation of the rotor, which
may comprise of determining a primary direction of the tip leakage
air flow relative to a blade tip chord, positioning a plurality of
elongated sealing members on a radially outward facing surface of
the blade tip at an angle substantially perpendicular to the
primary direction of the tip leakage air flow, and spaced along the
blade tip chord to effect an overlap of adjacent sealing members in
the direction of the tip leakage air flow.
[0011] One embodiment of the method may comprise positioning a
blade tip platform over the blade tip, the blade tip platform
having a surface facing the casing and extending at least between
the distal edges of the pressure side and suction side of the blade
and from the midchord toward the leading edge and trailing edge of
the blade. Another embodiment of the method may comprise the blade
tip platform extending to the leading edge and trailing edge of the
blade. Yet another embodiment of the method may comprise
positioning the elongated sealing members to effect uniform spacing
between the members along the blade tip chord. An embodiment of the
method may also comprise positioning the elongated sealing members
to effect non-uniform spacing between the members along the blade
tip chord. A further embodiment of the method may comprise
positioning the elongated sealing members to effect greater spacing
between the members near the edges of the blade relative to the
spacing between members near the mid-chord of the blade. A further
embodiment may also comprise positioning the elongated sealing
members to effect greater spacing between the members near the
mid-chord of the blade relative to the members near the edges of
the blade.
[0012] An embodiment of the method may comprise positioning a
plurality of elongated sealing members having a uniform radial
dimension. Another embodiment of the method may comprise
positioning a plurality of elongated sealing members having a
differing radial dimension. Yet another embodiment of the method
may comprise positioning a plurality of elongated sealing members
each having a varying radial dimension along the length thereof. An
embodiment of the method may also comprise providing an abradable
region on the casing adjacent the blade tip, dimensioning the
sealing members in the radial direction to effect contact between
at least a portion of each sealing member and the abradable region;
and rotating the rotor to effect rub between the plurality of
sealing members and the abradable region, wherein said rub causes a
plurality of annular channels to be formed in the abradable region
with each one of said plurality of annular channels corresponding
to a respective one of said plurality of sealing members.
[0013] Yet another aspect of the rotor assembly having a casing, a
rotor encased by the casing, and a rotor blade coupled to the rotor
having a blade tip spaced from the casing, may be a method of
reducing a tip leakage air flow between the blade tip and the
casing from a pressure side of the rotor blade to a suction side of
the rotor blade during rotation of the rotor, comprised of
positioning a blade tip platform over the blade tip with a surface
facing the casing and extending at least between the distal edges
of the pressure side and suction side of the blade and between the
leading edge and trailing edge of the blade, positioning a
plurality of elongated sealing members on the surface of the blade
tip platform having a selected lateral cross-sectional shape at a
selected angle relative to the blade tip chord and being spaced in
a selected chord-wise spacing pattern along the blade tip chord,
determining the flow rate and direction of the tip leakage airflow,
and varying one or more of the selected lateral cross-sectional
shape, the selected angle relative to the blade tip chord, and the
selected chord-wise spacing pattern to effect a change in the flow
rate of the tip leakage air flow.
BRIEF DESCRIPTION OF THE DRAWINGS
[0014] The following will be apparent from elements of the figures,
which are provided for illustrative purposes and are not
necessarily to scale.
[0015] FIG. 1 is a schematic and sectional view of a portion of a
blade and casing of a turbine engine.
[0016] FIG. 2 is an isometric view of a blade of a turbine
engine.
[0017] FIG. 3 is a schematic and sectional view of a rotor assembly
having a blade encased in a casing of a turbine engine.
[0018] FIGS. 4A and 4B are isometric views of a blade tip sealing
portion that forms the distal end of a blade of a turbine engine in
accordance with some embodiments of the present disclosure.
[0019] FIG. 5 is a schematic and sectional view of sealing members
of a blade tip sealing portion configured to contact the radially
inner surface of a casing in accordance with some embodiments of
the present disclosure.
[0020] FIG. 6 is a schematic and sectional view of sealing members
of a blade tip sealing portion configured to extend into and
contact an abradable region of the casing in accordance with some
embodiments of the present disclosure.
[0021] FIG. 7 is a schematic and sectional view of sealing members
of a blade tip sealing portion extending into annular channels
pre-formed in an abradable region of the casing in accordance with
some embodiments of the present disclosure.
[0022] FIG. 8 is a schematic and sectional view of a plurality of
sealing members extending radially inward from the casing to
contact the blade tip, in accordance with some embodiments of the
present disclosure.
[0023] FIGS. 9A and 9B are profile views of a blade tip in
accordance with some embodiments of the present disclosure.
[0024] FIG. 10 is a schematic and sectional view of sealing members
of a blade tip sealing portion configured to contact the radially
inner surface of a casing in accordance with some embodiments of
the present disclosure.
[0025] FIG. 11 is a schematic and sectional view of sealing members
of a blade tip sealing portion configured to contact the radially
inner surface of a casing in accordance with some embodiments of
the present disclosure.
[0026] FIG. 12 is a schematic and sectional view of sealing members
of a blade tip sealing portion having varying geometries in
accordance with some embodiments of the present disclosure.
[0027] While the present disclosure is susceptible to various
modifications and alternative forms, specific embodiments have been
shown by way of example in the drawings and will be described in
detail herein. It should be understood, however, that the present
disclosure is not intended to be limited to the particular forms
disclosed. Rather, the present disclosure is to cover all
modifications, equivalents, and alternatives falling within the
spirit and scope of the disclosure as defined by the appended
claims.
DETAILED DESCRIPTION
[0028] For the purposes of promoting an understanding of the
principles of the disclosure, reference will now be made to a
number of illustrative embodiments illustrated in the drawings and
specific language will be used to describe the same.
[0029] This disclosure presents embodiments to overcome the
aforementioned deficiencies in fan, compressor, and turbine blades
of a turbine engine. More specifically, the present disclosure is
directed to systems and methods for reducing or eliminating leakage
through the blade tip clearance. The present disclosure is directed
to sealing mechanisms for the clearance between the blade tip and
casing in a fan, compressor, or turbine of a turbine engine.
[0030] FIG. 2 is an isometric view of a blade 101 of a turbine
engine. Blade 101 comprises a root portion 120 and a main airfoil
body 122. Root portion 120 may be configured to engage a rotor or
other shaft and disc assembly. The main airfoil body 122 extends
radially outward from the root portion 120 and terminates at a
distal end in the blade tip 109. The airfoil body 122 comprises an
first side surface 124 and a second side surface 126, each of which
extend between a leading edge 128 and trailing edge 130. In some
embodiments, as when the present disclosure is applied to a blade
101 of a turbine, the first side surface 124 is a pressure side
surface and the second side surface 126 is a suction side surface.
In other applications the location of the pressure and suction
sides may be reversed.
[0031] FIG. 3 is a schematic and sectional view of a blade 101 of a
turbine engine encased by a casing 103. The structure illustrated
in FIG. 3 may be referred to as a rotor assembly, which comprises
casing 103, a rotor 132 encased by the casing 103, and at least one
rotor blade 101 coupled to rotor 132. Blade 101 is coupled to a
rotor 132 or disc that is coupled to a rotatable shaft 134. The
blade tip 109 is spaced radially inward from the casing 103,
resulting in a blade tip clearance 105 or gap between the blade tip
109 and casing 103. An axis of rotation for the rotatable shaft
134, rotor 132, and blade 109 is depicted as dashed line A.
[0032] FIGS. 4A and 4B present isometric views of the blade tip
sealing portion 140 that forms the distal or radially outward end
of a blade 101. Blade tip sealing portion 140 comprises a blade tip
platform 142 and a plurality of sealing members 144 extending from
the blade tip platform 142.
[0033] Blade tip platform 142 comprises a surface 143 that faces
the casing 103 and extends at least between the distal edges of the
second side surface 126 and the first side surface 124 of said main
airfoil body 122. In some embodiments blade tip platform 142
comprises a flange 146 or lip that extends beyond leading edge 128,
trailing edge 130, first side surface 124, and/or second side
surface 126. In addition to providing support for the plurality of
sealing members 144, blade tip platform 142 improves the stiffness
or rigidity of blade tip 109, with improved performance of the
blade 101 in regards to resistance of bending and untwist. In some
embodiments blade 101 and blade tip platform 142 are integrally
formed.
[0034] A plurality of sealing members 144 extend radially outward
from blade tip platform 142. Sealing members 144 may be referred to
as ridges, rails, or protrusions. In some embodiments sealing
members 144 may be elongate structures positioned on surface 143 of
blade tip platform 142 and extending between the distal edges of
first side surface 124 and second side surface 126. As explained
further below with reference to FIGS. 9A and 9B, the plurality of
sealing members 144 may be positioned on the blade tip platform 142
to extend between a pressure side edge 148 and a suction side edge
150 at an angle substantially perpendicular to an air flow leakage
across the blade tip platform 142. The plurality of sealing members
144 may also be spaced between the leading edge 128 and the
trailing edge 130 of the main airfoil body 122 to effect overlap of
adjacent sealing members 144 in the direction of the air flow.
[0035] The height, spacing, angle (relative to the axis of rotation
or relative to a pressure side or suction side of the blade),
thickness, and quantity of sealing members 144 may be optimized
based on the specific application of the disclosed blade tip
sealing portion 140. Sealing members 144 may have any number of
shapes, profiles, heights, circumferential widths, spacing, and
variability of geometries along the blade tip. Some examples of the
lateral cross-sectional shapes of the members are shown in FIG. 12.
In some embodiments the sealing members 144 further comprise a high
temperature coating. In some embodiments, such as that shown in
FIGS. 4A and 4B, sealing members 144 are spaced equally along the
chord of the blade tip 109, are similarly shaped as rounded ridges,
and are identically angled relative to an axis of rotation or a
primary leakage vector.
[0036] In some embodiments sealing members 144 are positioned on
surface 143 to effect uniform spacing between the members 144 along
the blade tip chord. In other embodiments sealing members 144 are
positioned on surface 143 to effect non-uniform spacing between the
members 144 along the blade tip chord.
[0037] In some embodiments sealing members 144 are positioned on
surface 143 to effect greater spacing between the members 144 near
the leading edge 128 and trailing edge 130 relative to the spacing
between members 144 near the mid-chord of blade tip 109. In some
embodiments sealing members 144 are positioned on surface 143 to
effect greater spacing between the members 144 near the mid-chord
of blade tip 109 relative to the spacing between members 144 near
the leading edge 128 and trailing edge 130.
[0038] In some embodiments sealing members 144 positioned on
surface 143 have a uniform radial dimension and lateral
cross-sectional shape. In other embodiments sealing members 144
positioned on surface 143 have a non-uniform or differing radial
dimension and lateral cross-sectional shape. In some embodiments
sealing members 144 positioned on surface 143 have a uniform radial
dimension along the length of the sealing members 144. In other
embodiments sealing members 144 positioned on surface 143 have a
non-uniform or varying radial dimension along the length of the
sealing members 144.
[0039] In some embodiments the sealing members 144 of a blade tip
sealing portion 140 are configured to contact the radially inner
surface of casing 103. FIG. 5 is a schematic and sectional view of
such an embodiment. In FIG. 5, sealing member 144 are shown
extending from the blade tip platform 142 to the casing 103. In
other words, the sealing member 144 extend fully across the blade
tip clearance 105. By contacting the casing 103, the sealing
members 144 form a seal between the blade 101 and casing 103 and
therefore reduce or eliminate leakage through the blade tip
clearance 105.
[0040] In some embodiments, the sealing members 144 of a blade tip
sealing portion 140 are configured to extend into and contact an
abradable region 155 of the casing 103. FIG. 6 is a schematic and
sectional view of such an embodiment. In FIG. 6, sealing member 144
are shown extending from the blade tip platform 142 into an
abradable region 155. The abradable region 155 forms a portion of
the casing 103 radially outward from blade 101. In some
embodiments, abradable region 155 may be replaced with a metallic
honeycomb seals that have improved performance at high
temperatures. In some embodiments the honeycomb seals comprise a
high temperature coating.
[0041] As the blade 101 rotates during operation of the turbine
engine, sealing members 144 contacting the abradable region 155
will likely rub annular pathways into the abradable region 155 that
correspond to each sealing member 144. Contact between the
abradable region 155 of casing 103 and one or more sealing members
144 forms a seal that reduces or eliminates leakage through the
blade tip clearance 105.
[0042] In some embodiments such as that illustrated in FIG. 6, an
existing fan, compressor, and/or turbine configuration is modified
to include blade tip sealing portion 140. In such an embodiment,
the blade tip clearance 105 need not be modified or reduced.
Rather, the blade tip sealing portion 140 may be included with a
blade 101 such that blade tip clearance 105 is substantially sealed
by the blade tip sealing portion 140.
[0043] In some embodiments sealing members 144 may extend into
annular channels 157 pre-formed in an abradable region 155 of
casing 103 and/or the casing 103 itself. FIG. 7 is a schematic and
sectional view of such an embodiment. As seen in FIG. 7, an
abradable region 155 forms a portion of casing 103 radially outward
from blade 101. The abradable region 155 in this embodiment
comprises a plurality of annular channels 157, with each channel
157 corresponding to a respective one of a plurality of sealing
members 144. Each sealing member 144 extends radially outward from
the blade tip sealing platform 142 into a respective channel 157 of
the abradable region 155. In some embodiments, at least a portion
of a sealing member 144 contacts at least a portion of the
abradable region 155, thereby forming a seal that reduces or
eliminates leakage through blade tip clearance 105. In other
embodiments, the configuration of sealing members 144 and channels
157 forms a torturous flowpath that reduces leakage through the
blade tip clearance 105.
[0044] In implementing the embodiment of FIG. 7, care must be taken
in that any axial excursion of the blade 101 could cause sealing
members 144 to rub and widen the annular channels 157. This
widening could degrade the effectiveness of blade tip sealing
portion 140. Axial excursions could be caused, for example, by
untwisting of blade 101, shifts in axial position by the rotatable
shaft 134 or rotor 132, surges, and the like.
[0045] In some embodiments a plurality of sealing members 161
extend radially inwardly from the radially inner surface 107 of the
casing 103. FIG. 8 is a schematic and sectional view of such an
embodiment. In FIG. 8, a blade tip sealing portion 160 comprises a
plurality of sealing members 161 that extend from the casing 103 to
the blade tip platform 142. Sealing members 161 are configured to
contact the blade tip 109 of blade 101. In other words, the sealing
members 161 extend fully across the blade tip clearance 105. By
contacting the blade tip 109, the sealing members 161 form a seal
between the blade 101 and casing 103 and therefore reduce or
eliminate leakage through the blade tip clearance 105.
[0046] In some embodiments, a blade tip sealing portion 140
comprises a plurality of sealing members 144 as illustrated in FIG.
10. The plurality of sealing members 144 may extend from the tip
109 of the blade 101, and the blade tip platform may be omitted. In
some embodiments the plurality of sealing members 144 extend from a
radially outward facing surface of the blade 101 or blade tip
109.
[0047] In some embodiments, such as that illustrated in FIG. 11,
the blade tip sealing portion 140 may extend chordwise from the
midchord in the direction of the leading edge 128 and trailing edge
130 but not extend fully to the leading edge 128 and/or trailing
edge 130. In other words, the blade tip sealing portion 140 may be
chordwise limited and may not extend from the leading edge 128 to
the trailing edge 130.
[0048] In some embodiments, sealing members 144 may be positioned
substantially perpendicular to a primary leakage vector V, or
substantially perpendicular to a primary direction of the tip
leakage air flow indicated by the direction of arrow V. FIG. 9A is
a profile view of a portion of a blade tip 109, illustrating a
plurality of leakage vectors from a pressure side 124 to a suction
side 126 across the blade tip 109. FIG. 9A shows a plurality of
leakage streams 170 that cross over the blade tip 109 (i.e. pass
through the blade tip clearance 105) with the steams 170 having a
common vector (indicated by arrow V) or at a minimum in a common
direction (the direction indicated by arrow V). In some
embodiments, a primary direction of tip leakage air flow is
determined relative to the blade tip chord. In some embodiments a
leakage flow rate is also determined.
[0049] FIG. 9B is a profile view of a portion of a blade tip 109
having a plurality of sealing members 144 extending therefrom. As
shown in FIG. 9B, sealing members 144 may be spaced between the
leading edge 128 and the trailing edge 130 of the blade tip 109 to
effect overlap of adjacent sealing members 144 in the direction of
the air flow. In other words, any leakage stream contacting the
pressure side surface 124 at the leakage vector or direction
indicated by arrow V will be blocked from reaching the suction side
surface 126 by at least one sealing member 144 and, due to the
overlap of adjacent sealing members 144, may be blocked by more
than one sealing member 144. Chord-wise spacing of the sealing
members 144 is sufficient to present an overlapping geometry to the
primary direction of tip leakage air flow at operating
conditions.
[0050] In some embodiments, the angle of each sealing member 144
may be measured relative to the axis of rotation of the turbine
engine, fan, compressor, and/or turbine. In some embodiments, each
sealing member 144 is positioned along the blade tip 109 to have a
unique angle compared with other sealing members 144 positioned
along that blade tip 109. The angle may be measured relative to a
leakage vector or the axis of rotation. In some embodiments, one or
more sealing members 144 positioned along the blade tip 109 may
have an angle that is different from the angle of another sealing
member 144 positioned along that blade tip 109. The angle may be
measured relative to a leakage vector or the axis of rotation.
[0051] In some embodiments the angle of each sealing member 144
positioned along the blade tip 109 is adjusted to be perpendicular
to the direction of primary leakage at that particular chord-wise
position. Similarly, in some embodiments the shape of each sealing
member 144 positioned along the blade tip 109 is optimized based on
the direction of primary leakage at that particular chord-wise
position.
[0052] The present disclosure additionally provides methods for
reducing or eliminating leakage through the blade tip clearance 105
in a fan, compressor, or turbine of a turbine engine. A primary
direction of tip leakage air flow is determined relative to a blade
tip chord. A blade tip platform is positioned over the blade tip.
As described above, the blade tip platform 142 has a surface 143
facing the casing 103 and extending between the distal edges of the
pressure side 124 and suction side 126 of blade 101, as well as
between the leading edge 128 and trailing edge 130 of blade 101. A
plurality of sealing members 144 are positioned on the surface 143
of the blade tip platform 142. As described above, the sealing
members 144 may be positioned at an angle substantially
perpendicular to the primary direction of tip leakage air flow.
Sealing members 144 may also be spaced along the blade tip chord to
effect overlap of adjacent sealing members 144 in the direction of
the tip leakage air flow.
[0053] In another method of the present disclosure, the method
comprises positioning a blade tip platform over the blade tip,
positioning a plurality of elongated sealing members on the surface
of the blade tip platform, and rotating the rotor or effect rub
between the plurality of sealing members and the abradable region.
As discussed above, the blade tip platform having a surface facing
the abradable region of the casing and extending at least between
the distal edges of the pressure side and suction side of the blade
and between the leading edge and trailing edge of the blade. The
sealing members are dimensioned such that at least a portion of
each sealing member contacts the abradable region. The rub of
sealing members against the abradable region 155 causes a plurality
of annular channels to be formed in the abradable region with each
one of said plurality of annular channels corresponding to a
respective one of said plurality of sealing members.
[0054] In some embodiments the method further includes determining
a primary direction of the tip leakage air flow relative to a blade
tip chord. In some embodiments the method further includes
positioning the plurality of elongated sealing members on the
surface of the blade tip platform at an angle substantially
perpendicular to the primary direction of the tip leakage air flow.
In some embodiments the method further includes positioning the
plurality of elongated sealing members on the surface of the blade
tip platform at a spacing along the blade tip chord to effect
overlap of adjacent sealing members in the direction of the tip
leakage air flow.
[0055] In still another method of the present disclosure of
reducing blade tip clearance leakage, the method comprises
positioning a blade tip platform over the blade tip, positioning a
plurality of elongated sealing members on the surface of the blade
tip platform, determining the flow rate and direction of the tip
leakage airflow, and varying one or more of the selected lateral
cross-sectional shape, the selected angle relative to the blade tip
chord, and the selected chord-wise spacing pattern to effect a
change in the flow rate of the tip leakage air flow.
[0056] As described above, the blade tip platform has a surface
facing the casing and extending at least between the distal edges
of the pressure side and suction side of the blade and between the
leading edge and trailing edge of the blade. The plurality of
elongated sealing members that are positioned on the blade tip
platform before the step of determining flow rate and direction of
the tip leakage airflow have a selected lateral cross-sectional
shape, are positioned at a selected angle relative to the blade tip
chord, and are spaced in a selected chord-wise spacing pattern
along the blade tip chord.
[0057] The present disclosure provides systems and methods for
reducing leakage through the blade tip clearance 105. The
disclosure is applicable to fan, compressor, and turbine blades of
a turbine engine. In some embodiments, the present disclosure may
be applied to certain stages of a compressor or turbine but not to
all stages. The advantages realized by the present disclosure are
most advantageous in compressor blade systems, where the clearance
to span ratio is more favorable for the benefit. For example, at
higher clearance to span ratios the importance of reducing leakage
is increased.
[0058] The present disclosure provides many advantages over
previous blade and blade tip clearance designs. Most notably, the
present disclosure significantly reduces or even eliminates leakage
across the blade tip clearance. Decreasing such leakage improves
efficiency of the associated fan, compressor, or turbine and may
increase stall margin as well. Decreasing blade tip clearance
leakage also allows for consideration and optimization of other
design factors to meet various aero and mechanical
requirements.
[0059] Although examples are illustrated and described herein,
embodiments are nevertheless not limited to the details shown,
since various modifications and structural changes may be made
therein by those of ordinary skill within the scope and range of
equivalents of the claims.
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